Studies are continuing on the role of naturally occurring prostaglandins in the regulation of vascular function in rats, rabbits and dogs. The effects of prostaglandins and inhibitors of prostaglandin synthesis upon blood pressure, vascular reactivity, reactive and functional hyperemia, and development of tachyphylaxis are under investigation. Currently, we are also exploring the dependence of the renal circulation and function of dogs and rabbits on the intra-renal generation of prostaglandins.